Combined Hydrothermal Liquefaction and Catalytic Hydrothermal Gasification System and Process for Conversion of Biomass Feedstocks

ABSTRACT

A combined hydrothermal liquefaction (HTL) and catalytic hydrothermal gasification (CHG) system and process are described that convert various biomass-containing sources into separable bio-oils and aqueous effluents that contain residual organics. Bio-oils may be converted to useful bio-based fuels and other chemical feedstocks. Residual organics in HTL aqueous effluents may be gasified and converted into medium-BTU product gases and directly used for process heating or to provide energy.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from U.S. Provisional PatentApplication No. 61/657,416 filed 8 Jun. 2012 entitled “CombinedHydrothermal Liquefaction and Catalytic Hydrothermal Gasification forConversion of Biomass Feedstocks”, which reference is incorporatedherein in its entirety.

STATEMENT REGARDING RIGHTS TO INVENTION MADE UNDER FEDERALLY-SPONSOREDRESEARCH AND DEVELOPMENT

This invention was made with Government support under ContractDE-AC05-76RLO-1830 awarded by the U.S. Department of Energy. TheGovernment has certain rights in the invention.

FIELD OF THE INVENTION

The invention relates generally to biomass conversion systems andprocesses. More particularly, the invention relates to a combinedhydrothermal liquefaction and catalytic hydrothermal gasification systemand process for conversion of biomass to suitable chemical feedstocksfor fuel production.

BACKGROUND OF THE INVENTION

Aqueous effluents released from hydrothermal liquefaction (HTL)facilities may contain byproducts that include dissolved organicmaterials. Organic materials in the aqueous HTL effluents may berelatively dilute (˜2% carbon by weight) but also represent a largevolume, constituting as much as 40% of the total carbon in the originalbiomass feedstock. Thus, recovery of these organic materials and reuseof the heated water stemming from these effluent streams is key tomaintaining overall energy efficiency of biomass conversion.Accordingly, new approaches for processing of these aqueous effluentstreams are needed. The present invention addresses these needs.

SUMMARY OF THE INVENTION

The present invention includes a combined hydrothermal liquefaction andcatalytic hydrothermal gasification (HTL-CHG) system for conversion ofbiomass to bio-oils and recovery and conversion of residual organics inaqueous effluent streams to bio-based fuels and other value-addedchemicals. The system may include a first hydrothermal liquefaction(HTL) stage that converts biomass in an aqueous medium at a temperatureand pressure selected to form a conversion product that includes aseparable bio-oil and an aqueous fraction containing residual organics.The aqueous fraction containing residual organics may be introduced asan effluent stream from the HTL stage reactor directly into a catalytichydrothermal gasification (CHG) stage reactor at a temperature andpressure selected to form a product gas containing at least onehydrocarbon or other medium BTU product gas. Combustion of the productgas may be performed to provide a net positive release of energy fromconversion of the biomass. Minerals obtained from the aqueous stream inthe CHG may be used as nutrients for growth of plants or another biomasssource from which biomass may be grown and harvested for use in anotherbiomass conversion cycle in the HTL-CHG system.

Heat exchangers may also be positioned to recover heat that preheatsbiomass feedstocks introduced to the HTL stage; to deliver heat toselected processes employed in conversion of biomass feedstocks in theHTL stage; to provide finishing heat needed to bring effluent streams tofull stage or process temperatures; to recover heat from various aqueousstream effluents that may be distributed to preheat biomass feedstocksintroduced to the HTL stage or process; to provide heat to other stagesemployed in the conversion of biomass feedstocks; to provide “finishing”heat needed to bring aqueous effluents to full stage processtemperatures; including combinations of these various purposes. Heatexchangers suitable for use include, but are not limited to, e.g.,counter-current heat exchangers; burner-type heat exchangers; make-upheat exchangers and heaters; and combinations of these various heatingdevices. No limitations are intended.

The present invention also includes a process for conversion of biomassto bio-oils suitable for generation of bio-based fuels,hydrocarbon-containing product gases (e.g., medium BTU gases), andminerals suitable for use as nutrients for growth of plant materials orother biomass sources. The process may include hydrothermally liquefying(HTL) a biomass in an aqueous medium at a temperature and pressureselected to form a conversion product including a separable bio-oil andan aqueous fraction containing residual organics. The process may alsoinclude catalytically and hydrothermally gasifying (CHG) residualorganics in the aqueous fraction released from the HTL stage or processat a temperature and pressure selected to form a product gas. Theproduct gas may contain at least one hydrocarbon or other medium BTUproduct gas. Combustion of the hydrocarbon product gas may be used toprovide a net positive release of energy from conversion of the biomass.

The biomass may be derived from plants, algae, photosyntheticcyanobacteria, animal waste, industrial food and liquid processingwastes (e.g., meat solids and dairy liquids), other biomass materials(e.g., wood), and combinations of these various biomass types. Algae maybe a macroalgae, a microalgae, or a combination of a macroalgae and amicroalgae. Macroalgae may be a sea weed, kelp, or combinations ofvarious macroalgae sources.

Biomass-containing sources may include lignin, carbohydrates, proteins,lipids, triacylglycerides (TAGs), free fatty acids, and combinations ofthese various compounds. Bio-oil generated from biomass-containingsources in the HTL stage or process may include components derived fromlignin, carbohydrates, proteins, lipids, membrane lipids, phospholipids,triacylglycerides, free fatty acids, and combinations of these variouscompounds. Exemplary compounds present in bio-oils of the presentinvention include, but are not limited to, e.g., lipid-derivedhydrocarbons; cyclic hydrocarbons containing oxygen; carbohydrateconversion products, protein conversion products; cyclic oxygenatesderived from carbohydrates and proteins; derivatives of these variouscompounds; and combinations of these various compounds.

The biomass conversion system or process may be a continuous system orprocess or a batch-wise system or process. For example, liquefaction andgasification of the present invention may be performed in separatereactor stages concurrently or sequentially. Liquefaction may includeflowing biomass through an HTL stage or process. Gasification mayinclude flowing HTL effluents through a CHG stage or process. In someapplications, flowing biomass and HTL effluents may be performed with asingle pumping unit without a change in operating pressure.

The conversion product may be a mixture or dispersion containing aseparable bio-oil and a water fraction containing residual organics.Liquefaction may include separating the bio-oil from the aqueousfraction containing residual organics at a selected temperature andpressure. For example, in some applications, the hydrothermalliquefaction (HTL) stage or process may include an intermediateseparation of bio-oil generated in the HTL. The conversion productcontaining the combined bio-oil/water mixture or dispersion may beseparated in a separator and the separated aqueous phase containingresidual organics diverted to the CHG stage or process.

Separation temperatures may be selected between ambient and about 360°C. Separation pressures may be selected ambient and about 210atmospheres. Operations at the higher end of the range of temperatureand pressure, absent an intermediate cooling step, can result in higherprocess efficiencies, which are desirable, but not required. Separationmay include introducing the aqueous phase containing the residualorganics into a CHG stage or process for gasification therein.

The HTL stage or process may be coupled directly with the CHG stage orprocess such that the HTL stage and the CHG stage may operate at thesame temperature and pressure conditions. Liquefaction and gasificationare performed at temperatures and pressures that maintain a liquid waterphase in each of the process stages during operation. Liquefaction andgasification temperatures may be selected up to about 360° C., orbetween about 300° C. and about 360° C. Liquefaction and gasificationpressures may be selected up to about 210 atmospheres, or between about100 atmospheres and about 210 atmospheres. Operation of both the HTL andCHG stages at the same temperature and pressure can reduce need forre-heating and/or re-pressurizing of aqueous stream effluents releasedfrom the HTL stage to reaction conditions needed for gasification whenentering the CHG stage. Elimination of re-heating and re-pressurizing ofHTL effluents can override costs for processing dilute aqueous phasefractions containing residual organics released from the HTL. And, withthe energy requirement for pressurizing and heating absent orsignificantly reduced, the gasification product (e.g., medium BTU gashydrocarbon) obtained from in the CHG stage and process can provide anet positive release of energy upon combustion.

In some applications, pressurizing each of the liquefaction andgasification stages may be performed with a single pumping unit withouta change in operating pressure.

Gasification may involve recycling heat released from the CHG stage orprocess and providing heat to another HT liquefaction cycle and/or a CHgasification cycle. CHG can be an efficient method for recovering energyfrom organics present in water stream effluents. For example, residualorganic materials present in the water effluents released from the HTLstage or process may be converted in the CHG stage or process over acatalyst. Gasification catalysts employed in the CHG stage or processmay include, but are not limited to, e.g., ruthenium (Ru), rhodium (Rh),osmium (Os), nickel (Ni), copper (Cu), including combinations of thesecatalysts. The CHG stage or process may contain a hot, pressurized waterenvironment that yields a low-carbon number hydrocarbon product gas(so-called medium-BTU product gas) such as methane that may also containother gases such as carbon dioxide.

The product gas may include methane (CH₄) and/or a higher hydrocarbon,carbon dioxide, and less than 5% hydrogen by weight.

Conversion of the aqueous byproducts (effluents) containing residualorganics can maximize efficiency of biomass conversion in hydrothermalliquefaction and gasification facilities and processes.

Gasification of the residual organics in the aqueous phase released fromthe HTL in the CHG stage or process may yield a nutrient-rich aqueousphase that contains minerals, ammonium, and dissolved carbon dioxidesuitable for growing plants or algae from which a biomass feedstock maybe derived. Thus, the mineral-rich aqueous phase from the CHG may beused as a nutrient medium.

Evaporation of water from effluent streams exiting the HTL stage orprocess is not required before the effluents enter the CHG stage orprocess. Processing of aqueous hydrothermal liquefaction byproductsreceived from the HTL represents a new component in the processing artsfor energy recovery, as no other options for use of these aqueousbyproducts have been developed to date.

The purpose of the foregoing abstract is to enable the United StatesPatent and Trademark Office and the public generally, especially thescientists, engineers, and practitioners in the art who are not familiarwith patent or legal terms or phraseology, to quickly determine from acursory inspection the nature and essence of the technical disclosure ofthe application. The abstract is neither intended to define theinvention of the application, which is measured by the claims, nor is itintended to be limiting as to the scope of the invention in any way. Amore complete appreciation of the invention will be readily obtained byreference to the following description of the accompanying drawings inwhich like numerals in different figures represent the same structuresor elements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a combined HTL-CHG system for conversion of biomass tobio-oil and hydrocarbon fuel products according to one embodiment of thepresent invention.

FIG. 2 shows a flowsheet for upgrading HTL-derived bio-oils inaccordance with the present invention.

FIG. 3 shows an exemplary upgrade stage for upgrading HTL-derivedbio-oils in accordance with the present invention.

FIG. 4 is a plot showing exemplary bio-oil hydrocarbons upgraded inaccordance with the present invention to bio-based feedstockhydrocarbons suitable for use in a petroleum refinery.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

A combined hydrothermal liquefaction (HTL) and catalytic hydrothermalgasification (CHG) system and process are described for conversion ofbiomass to suitable bio-oils for generation of bio-based fuels, andresidual organics suitable for generation of energy-producing (so-calledmedium BTU) hydrocarbon-containing product gases that together maximizeefficiency of biomass conversion in hydrothermal and gasificationfacilities. The following description includes a best mode of thepresent invention. While preferred embodiments of the present inventionwill now be described in reference to conversion of biomass derived fromalgae, the invention is not intended to be limited thereto. For example,it will be apparent that various modifications, alterations, andsubstitutions to the present invention may be made. The invention isintended to cover all modifications, alternative constructions, andequivalents falling within the scope of the present invention as definedin the claims listed hereafter. Accordingly, the description ofexemplary embodiments should be seen as illustrative only and notlimiting.

FIG. 1 shows a combined Hydrothermal Liquefaction (HTL)-CatalyticHydrothermal Gasification (CHG) system 100 of the present invention.System 100 may include an HTL stage 25 and process that converts biomassto bio-oil and a CHG stage 80 and process that converts residualorganics in the aqueous effluent stream released from HTL stage 25 toenergy-producing (so-called medium BTU) hydrocarbon-containing productgas 72, as detailed hereafter. The term “residual organics” refers toorganic compounds that remain in the aqueous stream effluents releasedfrom the HTL stage after liquefaction and conversion of the biomassfeedstocks. The term “medium BTU product gas” as used herein means ahydrocarbon product gas containing between about 40% and about 70%methane with other gases (e.g., CO2) making up the difference. MediumBTU product gases are between “low BTU” gases containing below 10%methane down to no methane gas and “high BTU” gases containing greaterthan 70% methane up to 100% methane.

Biomass Feedstocks

Biomass feedstocks may be obtained from various plants and animalwastes, but are not intended to be limited to these exemplary sources.In some embodiments, algae may be used as a biomass feedstock. Algae hasadvantages as a biomass source including, e.g., high growth potential,high yields per unit area, algae can be introduced into the conversionsystem or process as a slurry without extraction or further processing,and the ease of gasification. Algae suitable for use include, but arenot limited to, e.g., non-lipid producing algae, filamentary algae,macroalgae, cyanobacteria, mixed algae, microalgae, diatoms, includingcombinations of these various algae. Exemplary and representative algaeinclude, e.g., Spirulina, Chara, Nannochloropsis, and like algae. Nolimitations are intended by the disclosure of these exemplary classes.All biomass feedstocks as will be employed by those of ordinary skill inthe art in view of this disclosure are within the scope of the presentinvention.

In some embodiments, biomass conversion may be performed using wholealgae or algae biomass after lipids are extracted, i.e., lipid-extractedalgae (LEA). With LEA feedstocks, gasification reactions in the CHGstage or process can be fast (<1 hour) and complete (>99%). Typical CHGyields when using LEA feedstocks may be on the order of ˜0.4 liters ofmethane per gram dry solids.

In some embodiments, algae biomass solids may be introduced in the HTLstage in an aqueous medium, e.g., as a slurry. In various embodiments,the slurry may contain up to about 35% biomass solids by weight. In someembodiments, the slurry may contain between about 20% and about 35%biomass solids by weight. No limitations are intended.

In some embodiments, biomass-containing feedstocks (sources) may includevarious organic materials including, but not limited to, e.g.,triacylglycerides (TAGs), free fatty acids (FFAs), other membrane lipidsincluding phospholipids, proteins, carbohydrates, starches, andcombinations of these feedstock materials.

Bio-oils derived from these biomass-containing sources (obtained uponconversion in the HTL stage) may include oils characteristic of thesevarious bio-derived materials including, but not limited to, e.g., freefatty acids, long-chain hydrocarbons and oxygenated cyclic hydrocarbons.In addition, starches, sugars, and proteins present within the cells ofthe biomass may be converted to bio-oil. No limitations are intended bythe disclosure of these exemplary compounds.

Hydrothermal Liquefaction (HTL) processing is a highly efficient methodof producing fuel from algae. HTL can produce bio-oils at a high yieldfrom both lipid-producing and non-lipid-producing algae. The bio-oilfraction and water fraction exiting from the HTL stage or process can beseparated into separate streams as detailed further herein. Because theHTL stage or process can produce bio-oil directly from any algae,TAG-producing algae required by conventional conversion systems are notrequired. And, when used, TAG-producing algae are converted to bio-oil,increasing the total oil yield. In addition, quality of the bio-oil maybe higher when the TAG content is higher, meaning less oxygen and acidcontent, which results in easier upgrading compared with bio-oilproduced from other biomass sources.

In FIG. 1, system 100 may include a biomass growth stage 2 (e.g., agrowth pond) where biomass including, e.g., algae or other plant-derivedbiomass feedstocks may be grown and harvested. Wet biomass 4 derivedfrom biomass growth stage 2 may be concentrated in a concentrator 6where excess water may be removed. In concentrator 6, a typical algaefeedstock concentration may be increased, e.g., from about 0.6 grams ofalgae or biomass per liter (e.g., as recovered from growth stage 2) toabout 100 grams algae or biomass per liter or better. However,concentrations suitable for use are not intended to be limited.

In the figure, the wet concentrated biomass feedstock 8 may beintroduced to HTL stage 25. In HTL stage 25, wet biomass feedstock 8 maybe introduced to HTL reactor 10. HTL reactor 10 may be a pressurizedreactor. Hydrothermal liquefaction (HTL) processing in HTL reactor 10may employ heat, pressure, and water to convert biomass feedstock 8containing various organic materials into a crude conversion product 12that includes separable bio-oil, water, and solids fractions. The term“separable” means each of the bio-oil, water, and solids fractions inconversion product 12 may be separated from the other fractions, e.g.,by gravity separation. When separated, bio-oil fractions may beconverted to usable bio-based fuels, residual organics in the waterfractions may be gasified in a downstream gasifier, and solids fractionscan be recycled, e.g., as detailed further herein.

Introduction of biomass as a wet feedstock 8 directly into HTL stage 25eliminates need for drying, solvent extraction, and recovery of solidsfrom extraction solvents. Total bio-oil yields obtained by the presentinvention can be higher than those obtained for processes requiringsolvent extraction as practiced in the conventional art. In addition,temperatures used in the HTL stage may be lower than those employed inconventional dry pyrolysis reactors.

Solids 16 present within the crude conversion product 12 containing,e.g., solids 16, bio-oil 22, and water 34 exiting HTL reactor 10 afterconversion of biomass 8 may be separated from conversion product 12,e.g., in a solids separation stage (solids separator) 14. The term“solids” as used herein means phosphorus-containing (P) solids,sulfate-containing precipitates, and/or solids containing insolubleminerals (e.g., Ca, Mg, Fe, etc.) obtained from aqueous stream effluents34 exiting HTL reactor 10. Separation of precipitates is detailed, e.g.,by Elliott in U.S. Pat. No. 8,241,605, which reference is incorporatedin its entirety herein.

Solids 16 recovered from solids separation stage 14 may be recycled,e.g., as nutrients back into growth stage 2 to feed new generations ofplants from which biomass feedstocks 8 may be derived. Solids separator14 may be positioned, e.g., after HTL stage reactor 10 upstream from CHGstage reactor 50 to remove solids 16 (e.g., minerals and other solids)that can poison catalysts used in CHG gasifier 50, but position is notintended to be limited.

Separation of solids 16 from crude conversion product 12 in solidsseparation stage 14 may yield a solids-free conversion product 18containing bio-oil 22 and water 34. Bio-oil 22 and water 34 present inconversion product 18 may be separated into a separate bio-oil 22fraction and an aqueous fraction 34 containing residual organics, e.g.,in a separation stage 20 disposed, e.g., downstream from separationstage 14.

Separators suitable for use in concert with the present invention arenot limited. Number and position of separators are also not limited.Separators may include, e.g., LUCID® separators available commercially(Pall Corp., Port Washington, N.Y., USA). In some embodiments,separators may include an internal geometry that promotes coalescing orenlargement of bio-oil droplets, with a discharge path for continuousseparation of discontinuous-phase droplets of the crude conversionproducts into individual bio-oil and water (aqueous effluent) fractions.In various embodiments, separators may be employed that areself-cleaning, and/or require no auxiliary utilities, electrostatics,controls, or chemical additives to function. In addition, separators mayalso employ hardware that is compatible with a broad range of fluids andresistant to various corrosive solids. Separators may also be employedthat have an enclosed separation stage that eliminates potential forodors or hazards reaching operators.

Aqueous effluent 34 containing residual organics released from HTL stage25 may be introduced directly into a catalytic hydrothermal gasification(CHG) stage 80 containing a catalytic (CHG) reactor 50. In CHG reactor50, residual organics present within aqueous feed 34 may be gasified andconverted over a gasification catalyst such as ruthenium (Ru) on acarbon (C) support into a raw product (e.g., a “medium BTU”) gascontaining methane (CH₄) and CO₂ that may be released in an effluentstream 60 from CHG reactor 50. Aqueous effluent 60 may also be rich inheat. Effluent 60 released from CHG stage 80 may be delivered to apressure release stage (or a pressure “let-down” stage) 62 wherepressure may be reduced and/or vented and where the raw product gas inthe effluent may be allowed to expand. Reduced pressure gas/liquideffluent 64 released from Pressure Release Stage 62 may be subsequentlydelivered to a gas/liquid separator 66 and separated into a rawhydrocarbon product gas 72 fraction that contains methane (or othermedium-BTU gas) and CO2, and an aqueous effluent 74 containing nutrients76. Raw hydrocarbon product gas 72 may be subsequently cleaned of CO2 toproduce a clean hydrocarbon product gas (e.g., methane) suitable for useas an energy-producing or combustion fuel.

Aqueous stream effluent 74 released from gas/liquid separator 66 afterprocessing of residual organics may be rich in nutrients 76. Nutrients76 may include, but are not limited to, e.g., dissolved gases includingCO2 and nitrogen (N) (e.g., in the form of ammonia); minerals such as,e.g., iron, copper, zinc, and like elements; sulfate; potassium (K),dissolved CO2, and/or other nutrients. Nutrients 76 present in aqueouseffluent 74 released from separator 66 may be recovered and/or recycled,e.g., by returning nutrients 76 into growth stage 2 to promote growth ofalgae or other biomass feedstocks. When stripped of nutrients 76,aqueous effluent 74 may be recycled or ultimately released as a cleanwater 78 fraction. No limitations are intended.

Carbon dioxide gas 70 dissolved or otherwise present in aqueous effluent74 released from CHG stage 80 may also be recycled. For example, aqueouseffluent 74 released from gas/liquid separator 66 may be saturated withCO2 70, which may be sparged into biomass growth stage 2 to promotegrowth of algae or other biomass feedstocks in another biomass growthcycle for harvesting and conversion in the HTL-CHG stage and process.CO2 gas 70 may also be recovered from effluent stream 74. No limitationsare intended.

In various embodiments, hydrocarbon product gases 72 separated fromeffluent stream 74 in the flowsheet may be used to generate processheat, to generate electricity, or to generate other chemicals. Forexample, hydrocarbon product gas 72 released from separator 66 may becleaner than biogas derived from anaerobic digesters or landfills andthus can be directly burned or upgraded to natural gas by removingcarbon dioxide present within effluent gas stream 72.

Biomass conversion system 100 or process may include one or more heatexchangers configured to maintain heat balance within the system. Whileheat exchangers and heaters are described herein, it should beunderstood that heat exchangers and heaters are optional. The presentinvention provides heat efficiencies that can eliminate need for burnersor heaters required to drive finishing and inter-stage heat exchangers.All uses of heat derived from process flows described herein as will beselected by those of ordinary skill in the art in view of the disclosureare within the scope of the invention. No limitations are intended.

Heat exchangers may be of a counter-current design to recover andredirect recovered heat as an input or addition to fluid streams atvarious points of entry to process flows described herein. Heatexchangers may also be of an energized design (e.g., fired or burnertype) that increase temperatures of fluids or effluent streams tosuitable stage process temperatures that can drive chemistries in theselected HTL or CHG stages. No limitations are intended.

In some embodiments, HTL effluent 34 containing residual organicsreleased from separator 20 may be introduced through a heat exchanger 57or a make-up heater 57, e.g., of a fired or burner-type positioned,e.g., downstream from HTL stage 25. Heat exchanger 57 may be configuredto supply heat lost from HTL effluent 34 in transit through separator 20or other system components after release from HTL stage 25. Make-upheater/exchanger 57 may bring temperature of aqueous effluent 34 back upto process temperatures needed for gasification in CHG stage 80.

In some embodiments, a heat exchanger 56, e.g., of a counter-currenttype may also be positioned, e.g., after CHG stage 80 to recover heatfrom effluent 60 after exiting CHG reactor 50. Recovered heat may bediverted or used to preheat biomass feedstock 8 introduced to HTL stage25, or to provide heat to other processes employed in conversion ofbiomass feedstock 8.

In some embodiments, bio-oils 22 separated from effluent stream 18 inseparator 20 may be fed through a heat exchanger 58 or a make-up heater58, e.g., of a fired or burner-type positioned, e.g., downstream fromHTL stage 25 to supply heat lost to bio-oil 22 after release from HTLstage 25 in transit through separator 20 or other system components. Insome embodiments, make-up heater/exchanger 58 may optionally bringtemperature of bio-oil 22 to a temperature required in an upgrade stage24 described hereafter.

Bio-oil 22 may be upgraded in upgrade stage 24 (e.g., a hydrotreatmentfacility) in a hydrogen atmosphere at selected pressures andtemperatures (e.g., up to about 400° C.) to yield a green crude 30.“Green crude” as the term is used herein means a bio-oil that whenupgraded is in a form suitable for introduction as a bio-based feedstockto a petroleum refinery for conversion or refinery processing tosuitable fuels including, e.g., diesel and gasoline. Green crude mayinclude exemplary compounds including, but not limited to, e.g., linearhydrocarbons, cyclic hydrocarbons, aromatic hydrocarbons, alkylatedforms of these various compounds, and combinations of these variouscompounds. No limitations are intended.

Green crude 30 released from upgrade stage 24 may represent only 10% ofthe mass of the input feedstock (assuming 20% solids in the feedstockand 50% conversion of solids to bio-oil), but may contain significantheat energy. As such, green crude 30 released from upgrade stage 24 maybe fed through a heat exchanger 59, e.g., of a counter-current typepositioned, e.g., downstream from HTL stage 25 to recover highertemperature heat from effluent 30 exiting upgrade stage 24. Highertemperature heat recovered in heat exchanger 59 may be diverted or usedto increase the temperature of preheated stream 8 after exiting heatexchanger 56 that is subsequently introduced to HTL stage 25 forprocessing therein. Heat recovered in heat exchanger 59 may also be usedto provide heat to other processes employed in conversion of biomassfeedstock 8.

In various embodiments, effluent gases released from CHG stage 80 mayalso be used to deliver finishing heat to biomass feedstocks 8introduced to HTL stage 25 and/or heat for inter-stage reheating ofeffluents between the HTL 25 and CHG stages 80. No limitations areintended.

HTL and CHG processes of the present invention are complementary andtogether achieve a high conversion of biomass to bio-based fuels. TheHTL stage or process produces both bio-oil and effluent water. In someembodiments, up to 50% of the biomass may be converted to bio-oil.Biomass remaining within the effluent water may be rich in energy andcan be recovered by CHG. For example, remaining biomass may be gasifiedin the CHG stage to methane and carbon dioxide. CHG can also providerecovery of plant nutrients as detailed herein. The HTL-CHG system ofthe present invention allows up to 85% of the feedstock carbon to berecovered as fuel, with the remainder being converted to carbon dioxide.As will be understood by those of ordinary skill in the art, the degreeof biomass conversion depends at least in part on the type of feedstockused. Thus, no limitations are intended.

TABLE 1 lists summary results for a combined HTL-CHG test conducted onwhole algae and biomass derived from algae.

TABLE 1 lists summary results for a combined HTL-CHG test.

HTL HTL CHG TOTAL CARBON Bio-oil Carbon Carbon Yield to Fuel Mass YieldYield Yield Products ITEM (%) (%) (%) (gas/liquid) (%) Whole 58 69 17 86Nannochloropsis salina Predicted* 41 50 24 74 *Predicted = yields fornon-lipid producing algae

Results show hydrothermal processing is a highly efficient method forproducing fuel from plant-derived feedstocks, algae being representativebut not exclusive. With tandem HTL-CHG operation, system 100 can providesignificant economies of scale, e.g., in heating (e.g., in concert withheat exchangers 56, 57, 58, and 59), pumping, and other systemcomponents not observed when HTL stage 25 or CHG stage 80 operate absentthe other. HTL can produce high yields of bio-oil from bothlipid-producing and non-lipid-producing algae. Results show that thecombined HTL-CHG system 100 currently provides a recovery of at leastabout 85% or more of the total biomass carbon in the form of usablefuels. Subsequent gasification of the bio-oil and residual organicsfraction obtained from the HTL effluent can be introduced in the CHGstage or process and produce additional fuel. In addition, nutrients inthe water fraction obtained from the CHG stage or process can berecovered and recycled, e.g., back to algae growth ponds. Furtheroptimization is envisioned.

Catalytic Gasification

Gasification of residual organics of any form in aqueous phase effluentsreleased from the HTL stage may proceed according to the reaction shownin Equation [1]:

C_(x)H_(y)O_(Z) +nH₂O→aCH₄ +bCO₂  [1]

The gasification reaction is an equilibrium controlled reaction that mayinvolve, e.g., steam reforming & methanation in the CHG reactor. Here,CHO designates the various hydrocarbons that may be released into theaqueous effluent from the CHG reactor. Variables x, y, z, n, a, and bcorrespond to various stoichiometric quantities of carbon, hydrogen,oxygen, water, methane, and carbon dioxide, respectively, that can enterthe effluent stream. As will be appreciated by those of ordinary skillin the art, hydrocarbons present within the aqueous effluents releasedfrom the HTL stage or process will depend at least in part on the sourceof biomass from which the hydrocarbons are derived. For example,organics stemming from algae biomass will have an HCO content, watercontent, methane content, and carbon dioxide content that differ fromorganics stemming, e.g., from LEA biomass, animal biomass, or otherbiomass sources. No limitation to any one class of hydrocarbons isintended.

Gasification (CHG) Catalysts

Gasification catalysts suitable for use may include, but are not limitedto, e.g., ruthenium (Ru), rhodium (Rh), osmium (Os), nickel (Ni), copper(Cu), including combinations of these catalysts.

Temperatures and Pressures

In various embodiments, temperatures and pressures may be maintainedthrough the HTL stage or process, through the various separator stages,and through the CHG stage or process.

In some embodiments, the HTL stage or process may be operated at atemperature up to about 350° C. and a pressure up to about 200 atm.Depending on these process conditions, and whether a catalyst is used,output from the HTL stage or process can be either a liquid or a gas.However, temperatures and pressures are not intended to be limitedprovided the aqueous medium contains at least some quantity of acondensed (i.e., liquid water) phase during conversion of the biomass.

In some embodiments, liquefaction and gasification may both be performedat a temperature up to about 350° C. (662° F.) and a pressure up toabout 200 atm. (3000 psi). In some embodiments, liquefaction andgasification may be performed at a temperature between about 300° C. andabout 360° C. and a pressure between about 100 atmospheres and up toabout 210 atmospheres.

In some embodiments, process conditions for HTL stage and CHG stage maybe identical so that effluent water from HTL stage may be introduceddirectly to the catalyst bed in CHG stage that avoids loss of heat andpressure and efficiently recovers energy remaining in the HTL effluentwater.

In some embodiments, gasification in the CHG stage may be performed at atemperature up to about 350° C. (662° F.) and a pressure up to about 200atmospheres (3000 psi). In some embodiments, gasification may beperformed at a temperature between about 300° C. and about 360° C. and apressure between about 100 atmospheres and about 210 atmospheres.

Upgrading HTL-Derived Bio-Oils

FIG. 2 shows an exemplary flowsheet and process for upgrading HTLderived bio-oils in accordance with the present invention. In thefigure, wet biomass 8 may be liquefied in an HTL reactor 10 describedpreviously in reference to FIG. 1, producing a biomass conversionproduct 12 containing, e.g., a mixture of solids, bio-oil, and water.Conversion product 12 may be separated in a separator 20 into a fractioncontaining solids 16 and a fraction containing bio-oil 22. Bio-oil 22released from separation stage (separator) 20 may be upgraded, e.g., byhydrotreating bio-oil 22 in a hydrotreatment stage (hydrotreater) 24over a suitable hydrotreatment catalyst that adds hydrogen underpressure, to form a green crude 30 containing various liquidhydrocarbons that may processed into suitable fuels including, e.g.,diesel and gasoline.

FIG. 3 shows an exemplary upgrade stage 24 for upgrading HTL-derivedbio-oils in accordance with the present invention. Bio-oils may beupgraded by hydrotreating the bio-oil to yield a green crudeoxygen-containing hydrocarbons in the bio-oil including, e.g., cyclicketones, furans, and phenols may be converted to linear hydrocarbons,cyclic hydrocarbons, and aromatic hydrocarbons with a carbon number inthe range from about C=6 to about C=45, as detailed further herein.

As shown in the figure, upgrade stage 24 may include a hydrotreatmentreactor (hydrotreater) 26 constructed, e.g., of stainless steel (e.g.,300 series stainless steel) to minimize corrosion. Volumes are notlimited. Hydrotreater 26 may be filled with a hydrogenation catalyst asdetailed herein. In the exemplary embodiment, hydrotreater 26 mayoperate in a continuous flow mode at a flow rate that optimizesefficiency, but operation is not limited thereto. For example, batchoperation may also be considered.

Hydrogen gas (excess) may be introduced into the hydrotreatment reactor26 through a catalyst bed therein, e.g., in a “trickle-bed” fashion. Gasproducts may proceed out of reactor 26 continuously while liquidproducts may be recovered, e.g., in one or more receivers 28. Receivers28 may be cycled online and offline in order to be alternately filledand drained. Pressure control may be maintained on the offgas streamsuch that liquids may be captured in receivers 28 and cooled atpressure. Liquid product may be recovered by depressurizing and drainingreceivers 28 while valved off-line.

In various embodiments, hydrotreating the bio-oil in hydrotreatmentstage (hydrotreater) 24 may be conducted at temperatures between about150° C. and about 450° C.

In various embodiments, feed rates for introducing bio-oil into thehydrotreatment reactor (hydrotreater) may be at a Liquid Hourly SpaceVelocity of from about 0.1 LHSV to about 1.5 LHSV, but flows areadjustable to maximize and optimize hydrogenation. Thus, LHSV rates arenot intended to be limited.

In some embodiments, hydrogen partial pressures in the hydotreater maybe from about 75 atm to about 150 atm. Total quantity of hydrogen (H₂)for upgrading a typical bio-oil may be from about 1 m³ to about 10 m³per liter of bio-oil. Upgrading HTL bio-oils of the present invention inthe hydrotreating stage and process can require less H₂ compared withconventional Fast Pyrolysis bio-oils.

Hydrotreating the bio-oil serves to remove heteroatoms such as sulfur(S), oxygen (O), and nitrogen (N) from hydrocarbons in the bio-oil. Forexample, hydrotreating the HTL bio-oil can remove oxygen, nitrogen, andsulfur heteroatom-containing compounds to part-per-million levels in thebio-oil. While results for algae-derived biomass are described herein,heteroatom concentrations depend at least in part on the source ofbiomass. For example, biomass derived from wood can have heteroatomcontents lower than that of algae-derived biomass by about an order ofmagnitude. Thus, no limitations on specific heteroatom contents areintended.

In some embodiments, the bio-oil (green crude) after upgrading may havean oxygen content below about 10 wt %. In some embodiments, the crudebio-oil may have an oxygen content between about 5 wt % and about 10 wt%. In some embodiments, the upgraded bio-oil may have an oxygen (O)heteroatom content after upgrading below about 1% by weight. In someembodiments, the upgraded bio-oil after upgrading may have an oxygen (O)heteroatom content below about 500 ppm at a current limit of detection.

In some embodiments, crude bio-oil from HTL may include a nitrogenheteroatom content at or below about 4 wt %. In some embodiments, thecrude bio-oil after upgrading may include a nitrogen heteroatom contentbelow 500 parts-per-million at a current limit of detection. Nolimitations are intended by these exemplary results.

In some embodiments, the crude bio-oil from HTL may include a sulfur ashigh as 0.4 wt %. In some embodiments, the upgraded bio-oil may have asulfur (S) heteroatom content after upgrading at or below about 50 ppmat a current limit of detection. No limitations are intended by theseexemplary results.

Hydrotreatment Catalysts

Hydrotreatment catalysts suitable for use in hydrotreating bio-oils maybe any catalyst employed for hydrotreating petroleum oils including, butnot limited to, e.g., sulfided cobalt (Co) catalysts, sulfidedmolybdenum (Mo) catalysts, and sulfided nickel (Ni) catalysts. Nolimitations are intended.

Crude Bio-Oil Hydrocarbons

FIG. 4 shows representative and exemplary hydrocarbons that may beobtained from upgraded (e.g., hydrotreated and/or hydrocracked)HTL-derived bio-oils in accordance with the present invention. Invarious embodiments, hydrotreated green crudes of the present inventionmay contain various hydrocarbons including, but not limited to, e.g.,linear hydrocarbons, cyclic hydrocarbons, aromatic hydrocarbons, andalkylated forms of these various hydrocarbon moieties similar to thosepresent within fossil crudes. Bio-based crudes of the present inventionare suitable for use as feedstocks in petroleum distillation refineriesand can be refined conventionally.

In some embodiments, hydrotreated bio-oil products may have volumes thatare about 90% to about 94% of those of the original bio-oil.

In some embodiments, bio-oils derived from biomass sources may behydrotreated and converted to bio-based green crudes of the presentinvention with carbon numbers from about C=6 to about C=45. In someembodiments, carbon numbers will be between about C=14 to about C=18. Inother embodiments, carbon numbers will be between about C=18 and aboutC=45.

In some various embodiments, bio-based green crudes may be converted outof system into high-grade (containing low heteroatom contents asdescribed hereinabove) bio-based fuels including, e.g., diesel, jetfuel, and gasoline.

As will be appreciated by those of ordinary skill in the art, given thediverse nature of biomass sources, various combinations and classes ofhydrocarbons can be expected with various carbon numbers. Thus, nolimitations are intended.

Chemical Oxygen Demand

Chemical Oxygen Demand (COD) is a measure of the quantity of residualorganics (also termed “waste byproducts”) present in effluent streamsexiting the CHG stage. COD measures the mass of oxygen consumed perliter of solution (in mg/L or ppm). Aqueous effluents released from theCHG stage can be tailored to yield a Chemical Oxygen Demand (COD) valuethat assesses the toxicity of water exiting the CHG stage so that it canbe reused or recycled back for another HTL cycle or CHG cycle or permitsultimate release of aqueous effluents. Reuse and recycling of theseaqueous effluents can maximize efficiency of the flowsheet. As anexample, recycling aqueous effluents back as an input to theliquefaction step can reduce costs of added alkali. COD values below1000 ppm are sufficiently high to allow sufficient flow rates foroperation, but are sufficiently low to allow reuse and recycle ofeffluents without toxicity to plant growth. No limitation in COD valuesis intended by the present flowsheets.

EXAMPLES

The following Examples provide a further understanding of the presentinvention.

Example 1 Conversion of Lipid Extracted Algae (LEA), Nannochloropsissalina

The system of FIG. 1 was used. A lipid-extracted algae (LEA) biomasscomposed of Nannochloropsis salina with triacylglycerides (TAGs) removedwas obtained commercially (Solix BioSystems, Ft. Collins, Colo., USA).The LEA algae biomass sample was made into a slurry containing ˜20% drysolids and 80% water. The biomass sample slurry was introduced as afeedstock into the HTL stage reactor. Additional bio-oil was produced inthe HTL stage from lipids, proteins, and carbohy

Example 2 Conversion of Whole Algae, Nannochloropsis salina

The system of FIG. 1 was used. Pressure was 3000 psig. A LHSV value ofabout 2 was used. Temperature was up to 360° C. Liquefaction in the HTLstage was performed without a catalyst. Catalyst in the CHG reactor wasa ruthenium (Ru)-on-carbon (Ru/C) catalyst. A whole algae samplecomposed of Nannochloropsis salina (Solix BioSystems, Ft. Collins,Colo., USA) frozen immediately after harvesting with no additionalextraction processing to remove lipids was introduced to the HTL. Thebio-oil/water mixture recovered from the conversion of the algae samplein the HTL stage run was separated into separate bio-oil fraction and awater fraction. Effluent water from the HTL containing residual organicswas introduced to the CHG and converted into methane. TABLE 3 listsresults from the HTL-CHG conversion of whole algae.

TABLE 3 lists results from the combined HTL-CHG test of whole algaesample.

DATA ITEM (%) Lipid content of whole algae 33 Lipid content from HTL as% of algae mass 58 Bio-oil from HTL as % algae AFDW 64 Percent of algaecarbon in HTL Bio-oil 69 Mass of organic residual in HTL effluent waterfraction 34 Percent of organic in effluent water fraction converted toCH4 50 Total carbon recovery as fuel (i.e., oil + CH4) 86

While exemplary embodiments of the present invention have been describedherein, it is to be distinctly understood that this invention is notlimited thereto but may be variously embodied to practice within thescope of the following claims. It will be apparent to those skilled inthe art that many changes and modifications may be made withoutdeparting from the invention in its true scope and broader aspects. Theappended claims are therefore intended to cover all such changes andmodifications as fall within the scope of the invention.

1-19. (canceled)
 20. A continuous biomass conversion process, comprisingthe steps of: providing a biomass conversion product comprising a biooil fraction and an aqueous fraction, wherein each fraction is separablefrom the other fraction; without the aid of gravitational separation,continuously separating the bio oil fraction from the aqueous fraction;and converting at least a portion of the aqueous fraction to a productgas containing a fuel gas.
 21. The process of claim 20, wherein prior tocontinuously separating the bio oil fraction from the aqueous fraction,further comprising removing solids from the biomass conversion product.22. The process of claim 20, further comprising combusting the productgas to generate power.
 23. The process of claim 20, wherein the productgas comprises one or more of methane, hydrocarbons with a carbon numbergreater than that of methane, and carbon dioxide, wherein the productgas optionally comprises less than 5% hydrogen by weight.
 24. Acontinuous biomass conversion process, comprising the steps of:providing a biomass conversion product comprising a bio oil fraction andan aqueous fraction, wherein each fraction is separable from the otherfraction; using centrifugal force, continuously separating the bio oilfraction from the aqueous fraction; and converting at least a portion ofthe aqueous fraction to a product gas containing a fuel gas.
 25. Theprocess of claim 24, wherein the separation is self-cleaning.
 26. Theprocess of claim 24, wherein the separation is performed within a closedstage.
 27. A continuous biomass conversion process, comprising the stepsof: providing a biomass conversion product comprising a bio oil fractionand an aqueous fraction, wherein each fraction is separable from theother fraction; altering the temperature to continuously separate thebio oil fraction from the aqueous fraction; and converting at least aportion of the aqueous fraction to a product gas containing a fuel gas.28. The process of claim 27, wherein the separation is self-cleaning.29. The process of claim 27, wherein the separation is performed withina closed stage.
 30. The process of claim 27, further comprisingmaintaining the pressure to continuously separate the bio oil fractionfrom the aqueous fraction.